Ahnert-Hilger G, Nürnberg B, Exner T, Schäfer T, Jahn R
Institut für Anatomie der Charité, Humboldt-Universität zu Berlin, Germany.
EMBO J. 1998 Jan 15;17(2):406-13. doi: 10.1093/emboj/17.2.406.
Secretory vesicles store neurotransmitters that are released by exocytosis. Their membrane contains transporters responsible for transmitter loading that are driven by an electrochemical proton gradient across the vesicle membrane. We have now examined whether uptake of noradrenaline is regulated by heterotrimeric G proteins. In streptolysin O-permeabilized PC 12 cells, GTP-analogues and AlF4- inhibited noradrenaline uptake, an effect that was sensitive to treatment with pertussis toxin. Inhibition of uptake was prevented by Galphao-specific antibodies and mimicked by purified activated Galphao2. No effect was seen when Galphao2 in its inactive GDP-bound form or purified activated Galphao1, Galphai1 and Galphai2 were tested. Down-regulation of uptake remained unchanged when exocytosis was inhibited by the light chain of tetanus toxin. Vesicular acidification was not affected whereas binding of [3H]reserpine was reduced by GTPgammaS and Galphao2. These data suggest that the monoamine transporter rather than the vacuolar ATPase is affected. We conclude that catecholamine uptake is controlled by Galphao2, suggesting a novel function for heterotrimeric G proteins in the control of neurotransmitter storage.
分泌囊泡储存通过胞吐作用释放的神经递质。它们的膜含有负责递质装载的转运体，这些转运体由跨囊泡膜的电化学质子梯度驱动。我们现在研究了去甲肾上腺素的摄取是否受异源三聚体G蛋白调节。在经链球菌溶血素O通透处理的PC12细胞中，GTP类似物和AlF4-抑制去甲肾上腺素摄取，该效应对百日咳毒素处理敏感。Gαo特异性抗体可阻止摄取抑制，纯化的活化Gαo2可模拟该抑制作用。当测试处于无活性GDP结合形式的Gαo2或纯化的活化Gαo1、Gαi1和Gαi2时，未观察到效应。当破伤风毒素轻链抑制胞吐作用时，摄取的下调保持不变。囊泡酸化未受影响，而[3H]利血平的结合被GTPγS和Gαo2降低。这些数据表明受影响的是单胺转运体而非液泡ATP酶。我们得出结论，儿茶酚胺摄取受Gαo2控制，提示异源三聚体G蛋白在神经递质储存控制中具有新功能。
